(A), (B) and (C ) are three non-cylic funtional isomers of a carbonyl compound with molecular formula `C_(4)H_(8)O`. Isomers (A) and (C ) give positive Tollen's test whereas isomer (B) does not give Tollens' test but gives positive iodoform test. Isomers (A) and (B) on reduction with `Zn(Mg)` | conc. HCl give the same product (D).
(a) Write the structures of (A), (B) ,(C) and (D).
(b) Out of (A), (B) and (C ) isomers, which one is least reactive towards addition of HCN ?

Explanation

According to available information, (A) , (B) and (C) are all non-cylic carbonyl compounds. Since (A) and (C) give positive Tollen's test, they must have an aldehydic group. As the isomer (B) does not respond to Tollen's test but gives positive iodoform test, it must be a methyl ketone. The structural formulae of the three isomers are

(b) Out of the isomers, (B) should be least reactive towards addition of HCN.